R/odds.ratio.r

In pegeler/samplesizeCMH: Power and Sample Size Calculation for the Cochran-Mantel-Haenszel Test

#' Create an odds ratio estimate from a 2-by-2 table of frequencies or proportions
#'
#' @param x A two-dimensional matrix or table containing frequencies or proportions.
#'
#' @return A numeric vector.
#' @examples
#' # Load in Titanic data from datasets package
#' data(Titanic, package = "datasets")
#'
#' # Get marginal table of survival by sex
#' marginal_table <- margin.table(Titanic, c(2, 4))
#' marginal_table
#'
#' # Compute odds ratio of marginal table
#' odds.ratio(marginal_table)
#'
#' # Get partial tables of survival by sex, stratified by class
#' partial_tables <- margin.table(Titanic, c(2, 4, 1))
#' partial_tables
#'
#' # Compute odds ratio of each partial table
#' apply(partial_tables, 3, odds.ratio)
#'
#' @author Paul W. Egeler, M.S.
#' @export
odds.ratio <- function (x) {
  stopifnot(identical(dim(x), c(2L, 2L)))
  as.vector(x[1, 1] * x[2, 2] / x[1, 2] / x[2, 1])
}